Fork set-up 101: If the fork (any fork) dives excessively under brakes or bottoms out, THE SPRINGS ARE TOO SOFT ! Amp-Research sells three different springs for this fork, and because it has one each side, you have six different combinations of spring rate to choose from. You also have seperate preload adjustment for each spring, so you can set them up to be progressive. You can also change the oil viscosity in the dampeners. These forks are the best design out there for mountain bikes, but they don't suffer fools at all. Follow the instructions and don't grease the pivots, they'll last well (longer than Rock Shock seals) and when they're worn, buy replacements and replace them. For exactly the same reason the FSR pivot works better than all the others, the F4 fork does too. It was designed by the same guy! However it doesn't look like a motocross fork, so piston envy will blur some riders' judgement.

Powered two wheelers require heavy dive under braking to shorten wheelbase, sharpen the geometry and weight the front tire for tighter turns, then it can stretch out on the straights for better stability, under power. Bicycles however require a more constant geometry as they're short enough already, and don't roost from the turns. The F4 fork maintains near constant geometry throughout its travel. It's non-slider design makes it very stiff and this is why it tracks so well through ruts. It's axel path is up and slightly forward, instead of backward like normal forks. This means it doesn't absorb forward energy as part of its action, and make climbing over roots and rocks much easier. Conventional forks also compress air inside their tubes towards then of their travel. This helps them not to bottom out, and gives them a progressive feel at the very top. The F4's use linkages to achieve a more linear ramping curve and thus a 100mm travel F4 for have the suspension characteristics of a 125mm travel telescopic fork.

Weaknesses: I don't trust this fork. Simple as that. I'm a light guy (65kg), and some would think this suspension is great for lighter riders, but, I just don't trust it. When you really hit the breaks the front of your bike will make a magnificent dive, almost throwing you off the bike. That's dangerous.

Bottom Line:

If you're a light rider it might be ok, but you need to learn how this fork reacts.

Strengths: Not many,even back in '97.I have to say,it did track very,very well compared to most telescoping forks(not my Z2 Atom 80 though).The workings of the shock are exposed so you can hose it off.Lightweight too(I weighed mine at 3 lbs even).

Weaknesses: Where does it begin?This fork does very little to inspire confidence(barring the tracking,which is excellent)and has a slew of maintenance issues.Under braking the fork DIVES,and dives hard--almost enough to throw you off the bike in sketchy situations.You'd expect a fork with an(advertised)100mm of travel to feel pretty plush,right?Well the F4 is anything but.It was bottoming quite a bit on even moderate hits,much more so on bigger hits.It simply hates stutter bumps,refusing to suck up the hits even slightly.It took small hits well,but most forks do that anyway,right?It also made an annoying wheeze on every impact.Beyond that,the fork is sketchily designed.The pivots stay tight for a little while,but after 3 months you can literally see how much side-to-side play it has.The bolts are mixed metric and non-metric--as a result you are constantly searching for the right wrench or socket to use.The fork is also a nightmare to work on.Its parts strip and break very easily.After 3 months,I finally got sick of this fork and sold it for a '97 Judy XC--yeah,a junky fork as well,but was at LEAST serviceable and really absorbed bumps.9 months or so later,the '97 AMP B-4 full suspension bike got sold as well for being a high-maintenance death trap.

Bottom Line:

Bad by '97 standards,still bad today.I could never get comfortable riding on this fork,and the maintenance issues reduce this good yet poorly executed concept to a worthless money pit.Avoid AMP products like the plague.

Strengths: Rigid laterally, light weight, tracks perfectly, and travel is just right, not too stiff-not too plush for XC! Mountain Bike Action magazine once called it the best fork they've ever ridden.

Weaknesses: Wish I had an adapter for Stnd Intl brakes that fit this fork, to install some XT Discs.

Bottom Line:

This fork rides the way a fork should! Its very maintenance friendly but doesn't require more maintenance than telescoping type forks. In my opinion, it looks pretty good too. AMP has always made some good stuff, you just have to apply a little labor to keep it in shape (sans the frame shocks).

MX TIP to preserve your AMP bushings: Go to your local hardware store and buy some Plumber's Thread Tape and Thread Anti-seize. The anti-seize should be the thick, pasty, silver stuff applied with a brush.Apply 3 or more wraps of thread tape around bolts where they go through bushings. This provides a little cushion between the bolt and the bushing; it also reduces wear and noise.If you have noisy pivots, first talk with AMP, their customer service is still very good. Otherwise, disassemble the affending pivot and apply a very light coating of anti-seize to the flat mating surfaces. Don't forget to reinstall the plastic waffer. Wipe away excess. A word of advice. Lubing your pivots will void your AMP warranty. My two AMP Research bikes are second-hand, older pieces that I maintain for myself and still in excellent condition.

Submitted by
michele varaschini
a Cross Country Rider
from villafranca (VR) italy

Date Reviewed: March 23, 2001

Bottom Line:

Hi. This is just an update on my last report. About a month ago I manged to obtain a RED shock spring with which I replaced the original green one. Now I have one red and one black, and the fork seems to work much better than before (by the way, I weigh about 73 kgs.). The change is not so evident in slow single track conditions, but handling and control are now much better in fast rocky conditions. The front wheel seems to follow the terrain better, and I have increased my speed on the same ol' downhill sections mainly because I feel more confident.Probably the original (green/black) spring combo was OK when the springs were new, but in fact they have both aquired some sag in these 5 years of use. The new red spring probably has helped bring things back to normal. Sooo, everything seems to be fine, but just a couple of days ago I ran across an Italian fork which really impressed me. It's a RACE FACTORY "Air Race"; can anyone tell me more about it? Cheers!!!

Submitted by
michele
a Cross Country Rider
from villafranca (vr) Italy

Date Reviewed: February 21, 2001

Strengths: Very light,easy to maintain (if you have the parts), allows very good control of front wheel, even when the terrain is quite rough. After 5 years of intensive use it's holding up quite well.Mine has the aluminum legs, by the way.

Weaknesses: Horst mixed metric and non-metric parts, making it difficult to obtain replacement bushings and pins, except if you purchase them from an AMP dealer. The aluminum hex screws are too soft and get damaged quite easily. Shock absorbers need to be refilled with oil every 6 months, if you want to have the fork performing well at all times.

Bottom Line:

I'm happy with the F4, and overall it probably does not require any more maintenance that other forks. I was about to decide to get a new fork, and this year's offerings seem to be better than in the past, but then I finally decided to keep the B4, at least for another year. After all, I use it mainly for XC (no races) and some fire road downhill, and it works well in these conditions. Occasionally I've had to face 1 meter drops, and even though I'm sure that the fork did bottom out, I didn't notice it doing so. I'm tempted to try a longer travel fork (10cm.)which should match the rear travel, but I'm afraid that I might end up being disappointed by the extra weight and excessive pogo-effect. The combination of frame and fork now allow me to face just about any type of trail condition without worry. I really have not noticed any excessive dive when braking or facing drops. In conclusion I wouldn't recommend anyone to buy a new one (can't count on AMP for help much longer), but in case you can get one cheap, I'd give it a try for XC use; you'll probably end up loving it. I'm happy with mine, and I'll be keeping it for quite a while, now that I've found out how to resolve the pin-and-bushings problem.

Weaknesses: AMP seems to be disappearing as a company. Good ol' Horst (boss/brains)has left California to live in his native Austria. Oh well. There are no AMP dealers left in Canada. Check the website.. they are selling truck-bed parts... hmmm, grab for cash?The fork could use more travel and better support. My fork has a non-standard disc mount... mebbe the new ones are standard.. check first.Most bike shops have no idea how to service one.

Bottom Line:

Would I recommend buying one?Well, no. Not any more. So: If you can convince yourself you can get service/parts for your fork (I bet AMP is outta business in 2-3 years)or you can service it yourself, and you are a mostly XC rider (forget it for monster drop-offs, and DH'ing), and need/want only 3 inches of usable travel, get one. But make sure you get a good deal. Me? I will be upgrading to a 4-5inch travel Marzocchi fork (Z1, Z2, MCR??) for 2001 season. I need more travel and a standard disc mount. The forks still are great, and I'm keeping them in case my fancy new Z1/Z2's suck.If you are over 180 lbs, be sure to get 2 RED springs. 165-180 go for red/black. 155-165 go black/black. 130-155 you can go green/green (lightest) or mebbe green/black. Go one size bigger than what you weigh, as the fork gets softer when the bushings break in. Need more info, email me toolbox@magma.ca

This fork broke 3 times. The first two times the fork broke at the dropout it was covered under warranty. Each time Amp would supposedly fix the problem with different leg material or bonding glue. The third break resulted in a serious crash. This product is dangerous and any serious cyclist will be risking their life using it. I through the fork away simply because I could not trust riding on it nor could I sell it to someone else in good conscience.

Submitted by
Christopher Davis
a Cross Country Rider
from Evergreen, Colorado, USA

Date Reviewed: May 21, 2000

Strengths: Amp first impressed me in 1994 with their B-3 frame and 2" fork. During the first few months AMP shocks work well. Eventually these shocks loss oil and begin to weeze. It is nice that AMP provides a minor exchange/upgrade but they have failed to resolved the maintenance issues. Nevertheless no other suspension fork tracks as well as AMP forks.

Weaknesses: Over the years,dealing with Bryan and others at AMP Research, I found they generally dont give a !@#$ about the inherit problems with their shocks. I have not gotten more than a hundred miles on either a rear shock or a front shock for the past several years. I have a second bike for my AMP is constantly needing maintenance. Recently, I have been snapping shafts in this F-4 fork. I have heard that AMP has recently decided not to manufacture this fork any longer, this comes to no surprize to me.

Bottom Line:

Dont be an AMP sucker, the F-4 should be recalled. I am not the only rider to be snapping shafts on these forks, yet they claim this has never occured before, yah!!!!!

I really love this fork, it's really fast & precise on tech twisty singletrack. When you roll over roots/logs it does not slow you down as telescopic forks do, doesnt feel twitchy even 3/4 compressed. The best comment I have heard: "I haven't seen that thing move". It does what it should, and it does it without being all that monkey buziness.

This is a best around 80+mm XC fork. It is not for freeriding/DH bombing, though it would take some abuse on rare occasions, 2-3' drops.

Now the bad staff. AMP shocks don't last, period. I blew mine after 3mo /2 of them winter, so not much riding/, and now I have to send my rear shock for rebuild.

They all suffer the same kind of failure: on medium intensity tech rides they overheat, oil expands and then it blows lower seals. I have spoken to Brian and he suggested to back up rear shock to give some room for expansion, but why me? can't you guys heat it to 180F and test before you decide how much oil needs to be there?

anyways I am not an aggressive rider, and I am only 140lbs, so durability is a question.

and putting this question aside I do like the fork, and I'd buy it even if I have to rebuild it every 3mo.

I am planning to have another post in a couple month to let you know how rebuild holds up.

This fork rocks! I got a good deal trading in my F1 using AMP's crash upgrade program. It's stiff, light, and has a long, smooth travel. It is stiff enough not to absorb energy or bob when pedaling, but cushy enough to absorb the bumps. I liked the F1 too, but this fork is an order of magnitude better. If you're looking for a great XC fork that will take you down hub-melting descents with ease, this is the fork for you. It looks cool too, and I like to think people are staring at it when I ride instead of my love blisters for a change.

I loved the fork, unfortunately it was stolen with my Klein not too long ago. I like my fork to be stiff and not exhibit bobbing while I'm climbing. There was a slight brake dive but much less than Marazocchis that I've seen. It's not the lightest fork out there anymore, others have just been playing catch up all these years. It is definitely one of the best XC forks that I've tried. It's light and responsive, handles the big bumps, roots extremely well. It's the perfect fork for XC. I'm thinking of running Hope hydrolic discs for my next bike otherwise I would buy another on a heart beat. Another thing that I find very important is Brian at Amp is very helpful and have always responded to all my emails and have shipped whatever spare parts I needed promptly. I highly recomment this fork for anyone looking for an XC orientated fork that's simple and light. If you're looking for an ultra plush, super sensitive, 5 foot drop offs fork then this is not the fork for you. However, if you're a rider who loves XC with tight twisty single track with a mix of fast fireroads and slow techinal clims, then you should take a look at this fork and give it a try if you can.Buy what fits your riding style and local terrain and you'll never be dissapointed. I know I did.

Just an update to my August 13, 1997 review. The fork is still just as light, tracks just as well, looks just as cool, and gets the job done -- but there is a price. Annual $100 rebuilds are getting old. I'm making my own boot this time to try and extend that maintenance period but my next rebuild may be my last.

Finally had a chance to get a few rides on the fork. I've ridden both Judy and some of her lesser cousins and was very dissapointed in how vague they all felt. I went with an Amp F-3 for a while and liked most of their qualities better than the Rock Shocks, stiff & light, but wished for greater (and smoother) travel. Got the F-4 on the new bike and love it. Fixed all the problems that I had with the F-3 and all the benefits too. Only minor complaint is that any fork in this range (Rock Shox, Manitou, or even Marz) for 3 inches of travel and about 3 pounds in weight is well over the $500 mark.

Related F4 Forum Posts

Hopefully I'm posting this question in the right section...
I have an 08' Cannondale F4. The stock headshock (fatty ultra) was rebuilt twice under warranty early on. It's been in storage for a few years. I recently pulled it out and it's junk again. I want to replace it. For the time being I'm goin ... Read More »

My stock tires on my 2008 F4 are in need of being replaced. Anyone have any suggestions? Any good "bang for the buck" tires?
Also, while I'm at it I wouldn't mind replacing the presta valves with schrader. Would I just need to drill out the rim a bit? I don't want it to look terrible.Read More »

I have a Joshua F4 that I am slowly raising from the dead. I have had it since 99 and I had a pretty bad wreck on it back in 2002 and it has been in pieces ever since. The bike is still in good condition, I was the one who took the blunt of the wreck. I love the bike and I am finally trying to bring ... Read More »

Hi, I've browsed this site in the past and recently, but having now purchased a 2nd hand F4, thought it was about time I joined.
the F4 I purchased isn't perfect, it was cheap and had sat a while before I got my hands on it, everything works fine and smoothly, but it is definitely worth me putting ... Read More »

I'm kind of stumped as right now I've been looking at both bikes. Wanted to get something that I can use for simple commuting in NY.
I want to stick with Cannondale so now I'm just trying to figure out which would end up being the better commuter.
I've rode both and I feel both have a nice feel t ... Read More »